What ID is needed to travel by air domestically in the US?

What ID should one show when travelling/buying air tickets in the US? What if the ID is an expired driver's licence, will that person be able to travel domestically or not? What IDs can be used?|||For domestic travel a photo ID like your Drivers License is adequate. However it is advisable to also carry your passport in case you are required to prove that you are a US citizen.|||You can still travel with an expired drivers license but you will go thru extra screening when you check in at the airport and go thru the security checkpoint.|||A valid state or government issued ID.